Sulfur mustard (2,2'-dichlorodiethyl sulfide; SM) is a potent vesicating chemical warfare agent that poses a continuing threat to both military and civilian populations. Significant SM injuries can take several months to heal, necessitate lengthy hospitalizations, and result in long-term complications affecting the skin, eyes, and lungs. This report summarizes initial and ongoing (chronic) clinical findings from SM casualties from the Iran-Iraq War (1980-1988), with an emphasis on cutaneous injury. In addition, we describe the cutaneous manifestations and treatment of several men recently and accidentally exposed to SM in the United States. Common, chronic cutaneous problems being reported in the Iranian casualties include pruritis (the primary complaint), burning, pain, redness, desquamation, hyperpigmentation, hypopigmentation, erythematous papular rash, xerosis, multiple cherry angiomas, atrophy, dermal scarring, hypertrophy, and sensitivity to mechanical injury with recurrent blistering and ulceration. Chronic ocular problems include keratitis, photophobia, persistent tearing, sensation of foreign body, corneal thinning and ulceration, vasculitis of the cornea and conjunctiva, and limbal stem cell deficiency. Chronic pulmonary problems include decreases in lung function, bronchitis with hyper-reactive airways, bronchiolitis, bronchiectasis, stenosis of the trachea and other large airways, emphysema, pulmonary fibrosis, decreased total lung capacity, and increased incidences of lung cancer, pulmonary infections, and tuberculosis. There are currently no standardized or optimized methods of casualty management; current treatment strategy consists of symptomatic management and is designed to relieve symptoms, prevent infections, and promote healing. New strategies are needed to provide for optimal and rapid healing, with the goals of (a) returning damaged tissue to optimal appearance and normal function in the shortest period of time, and (b) ameliorating chronic effects. Further experimental research and clinical trials will be needed to prevent or mitigate the acute clinical effects of SM exposure and to reduce or eliminate the long-term manifestations.